Mass spectra of linear and branched methyl(vinyl)siloxanes

The mass spectra of some linear and branched methyl(vinyl)siloxanes Me₃SiOSi(Me)(R)(OSiMeVin) _n Y (R=Vin, OSiMe₃; Y=OSiMe₃, Cl;n=0–2) were studied. The regularities of their fragmentation and an anomalously high probability of elimination of the ethylene molecule to form the stable 1,3-dioxa-2,4,6-trisilacyclohexane skeleton were revealed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 113–115, January, 1999.     

New preparative Grignard synthesis of (m-carboranylmethyl)siloxanes from chlorodimethylsiloxanes

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Inclusion complexes between cyclic siloxanes and cyclodextrins: synthesis and characterization

Molecular inclusion complexes between cyclodextrins and cyclic siloxanes were prepared and characterized via a combination of liquid and solid state NMR, FT-IR, TGA, powder X-ray diffraction, SEM–EDS and elemental analyses. The crystalline complexes adopted the channel-type conformation. Depending from the size of both the cyclic sugar cavity and the silicon guest, various yields (between 0 and 41%) and host–guest molar ratios (between 1:1 and 4:1) were obtained. α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) were observed to form crystalline inclusion complexes only with D₃ (cyclic dimethyltrisiloxane) due to steric effects, whereas the larger γ-cyclodextrin (γ-CD) formed inclusion complexes both with D₃, D₄ (cyclic dimethyltetrasiloxane) and D₅ (cyclic dimethylpentasiloxane). This study is believed to be the first step towards the selective removal of cyclic siloxanes impurities from commercial PDMS preparations.     

Efficient synthesis of (carboranylmethyl)siloxanes from carboranylcopper and chloromethylsiloxanes

A preparative synthesis of (carboranylmethyl)siloxanes from carboranylcopper and chloromethylsiloxanes was developed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 709–711, April, 1998.     

Addition reactions of linear siloxanes to allylamine

Russian Chemical Bulletin -     

New approach to the synthesis of cyclic 1,3-dithioacetals from thiophene-2-carbaldehydes

A highly selective method was developed for preparation of previously unknown 1,3-dithiolanes and 1,3-dithianes by reactions of thiophene-2-carbaldehyde and its analogs with alkanedithiols under the action of trimethylchlorosilane.     

Palladium(0) nanoparticle catalyzed cross-coupling of allyl acetates and aryl and vinyl siloxanes

The cross-coupling of allyl acetates and aryl and vinyl siloxanes proceeds readily by the catalysis of in situ generated palladium(0) nanoparticles. The reactions are stereoselective, and (E)-coupling products are obtained both from cis and trans allyl acetates. The coupling with vinyl siloxanes provides a novel protocol for the synthesis of 1,4-pentadienes.     

Determination of cyclic and linear siloxanes in soil samples by ultrasonic-assisted extraction and gas chromatography-mass spectrometry

A rapid method, based on sonication-assisted extraction in small columns (SAESC) and subsequent quantification and identification by gas chromatography-mass spectrometry (GC-MS), was developed for the determination of cyclic and linear siloxanes in soil. In the experiments with spiked samples (10-50 ng g(-1)), the recovery of cyclic and linear siloxanes ranged from 87.7 to 108.0% and from 84.9 to 107.6%, respectively. The validated method was used to determine the levels of these compounds in various types of soil samples collected from different locations in Spain. The cyclic siloxanes, decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6) were detected in all the soil samples analyzed at concentrations from 9.2 to 56.9 ng g(-1) for D5 and from 5.8 to 27.1 ng g(-1) for D6 in agricultural soils and from 22 to 184 ng g(-1) for D5 and from 28 to 483 ng g(-1) for D6 in industrial soils. The total linear siloxanes concentrations (L5-L14) (sum of the 10 congeners) ranged from 191 to 292 ng g(-1) in agricultural soils and from 1411 to 8532 ng g(-1) in industrial soils.     

New approach to the total synthesis of (-)-zeylenone from shikimic acid

The natural antitumor product (-)-zeylenone was prepared for the first time in a stereoselective synthesis from shikimic acid.     

New approach to the synthesis of tris(perfluoroalkyl)borane adducts with dialkylamines

A convenient synthetic approach to the adducts (C _n F_2n+1)₃BNHR₂ (n = 2–4, 6; R = Me, Et) was developed, based on the reaction of lithium perfluoroalkyls with dichloro(dialkylamino)boranes at temperatures below ?90°C. The target products can be synthesized with preparative yields of 50–90%.     

Preparation of co‐polymethyl(alkoxy)siloxanes by acid‐catalyzed controlled hydrolytic copolycondensation of methyl(trialkoxy)silane and tetraalkoxysilane

Polymethyl(alkoxy)siloxane copolymers, poly(MTES‐co‐TEOS), and poly(MTMS‐co‐TMOS), are prepared by acid‐catalyzed controlled hydrolytic co‐polycondensation of methyl(trialkoxy)silane MeSi(OR)₃ (R = Et (MTES) and Me (MTMS)) and tetra‐alkoxysilane Si(OR)₄ (R = Et (TEOS) and Me (TMOS)), respectively. The products are purified by fractional precipitation to provide polymethyl(alkoxy)siloxane copolymers with molecular weight 1000–10,000 (poly(MTES‐co‐TEOS)) or 1700–100,000 (poly(MTMS‐co‐TMOS)) that are stable to self‐condensation. These polymers are soluble in common organic solvents except for hexane, and form flexible and transparent free‐standing films with a tensile strength of 4.0–10.0 MPa. The structure of the polymethyl(alkoxy)siloxane copolymers is thought to be a random or a block co‐polymer. They are found to provide coating films with an adhesive strength up to 10, a refractive index of 1.36–1.40, and a dielectric constant of 3.5–3.6. The products also show better weathering stability than polyethoxysiloxane due to the hydrolytic polycondensation of TEOS. Field emission‐scanning electron micrography analysis reveals that coating films are composed of a micro‐phase separated structure. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4732–4741